The detection of physiologically-important molecules, such as metabolites, in a biological sample can be critical for monitoring a condition or a disease state of a subject. For example, the monitoring of glucose can be used to diagnose and manage diabetes, wherein maintaining blood glucose within a normal range of 70 to 120 mg/dL with insulin therapy and increased glucose monitoring can improve the long-term prognosis of subjects suffering from diabetes. Glucose levels alone, however, do not provide sufficient information for understanding the metabolic processes underlying diabetes and its development. The monitoring of fatty acids can provide an additional understanding of the events leading to the development of a pre-diabetic state or insulin resistance in a subject suffering from diabetes, particularly Type 2 diabetes. Similarly, energy metabolites, such as lactate, a byproduct of moderate exercise, can be monitored to assess the energy expenditure, exercise burden, or fatigue level of a subject.
One method for detecting metabolites, such as glucose, fatty acids, and lactate, includes conjugating a fluorophore, such as a fluorescent dye, with a binding member, i.e., a binding member of a specific binding pair, that has an affinity and specificity for a ligand, e.g., a metabolite of interest, and measuring a change in a fluorescent property of the fluorophore upon ligand binding. There is a need in the art, however, for improved fluorescent dyes for use as fluorophores in such systems. The presently disclosed subject matter addresses, in whole or in part, these and other needs in the art.